The electronic interaction of SnO2 with Ag and Pd particles dispersed on its surface was examined by means of X-ray photoelectron spectroscopy (XPS). The binding energies (BE) of Sn3d and O1s of Ag(1.5 wt%)-SnO2 and Pd(3.0 wt%)-SnO2, which were lower by 0.5–0.7 eV than those of pure SnO2 in the as-prepared state, shifted reversibly by reduction and oxidation treatments. These shifts in BE are shown to reflect the shifts of Fermi energy of SnO2 which are interacting electronically with the metal additives. The electronic interaction depended on the metal loading, being strongest at 1.5 wt% and 3.0 wt% loadings of Ag and Pb, respectively. The implication is that the electronic interaction is of primary importance to the inflammable gas detection by Ag-SnO2 sensors.

Electronic Interaction between Metal Additives and Tin Dioxide in Tin Dioxide-Based Gas Sensors : Surfaces, Interfaces and Films

Engineering mesoporous semiconducting metal oxides from metal-organic frameworks for gas sensing

Transition metal dichalcogenides (TMDs) have blazed a novel trail in the field of NO2 gas detection owing to the unique photoelectric properties and prospective gas sensing performance especially working at low operating temperature. However, the incomplete recoverability and susceptibility to humidity at room temperature restrict the practical applications of TMDs-based gas sensors. Herein, we demonstrate a fully recoverable WS2 based gas sensor with enhanced anti-humidity ability by combining the decoration of zero-dimensional PbS nanoparticles and the assistance of UV light. Through the control over the molar ratio of WS2/PbS, the optimized WS2/PbS (the molar is 10:1) gas sensor exhibits a remarkable elevated recovery rate from 33.4% to 99.8% with almost no baseline drift as compared to that in the pure WS2 gas sensor. More importantly, attributing to the irradiation of UV can accelerate the desorption of water molecules, WS2/PbS heterostructure based gas sensor manifests more stabilized anti-humidity performance with stable initial resistance and negligible response value drift (8.8%) in the range of 10%–90% relative humidity. Furthermore, UV-assisted WS2/PbS gas sensor also possesses prominent sensing performances including high sensitivity, low detection limit (∼20 ppb), favorable selectivity and outstanding long-term stability. This research will pave the way on designing high-performance TMDs-based gas sensors operating at room temperature.

UV-light-assisted NO2 gas sensor based on WS2/PbS heterostructures with full recoverability and reliable anti-humidity ability

Nanostructured metal oxide semiconductor-based gas sensors possess extensive applications due to relatively inexpensive, lightweight, long-lasting, robust, and high sensitivity and quick response and recovery times. Several strategies have been developed to enhance their sensing properties and meet the extended market demand for novel applications by modifying surface morphology, reducing particle size, and manipulating function.This work mainly concentrates on the systematic review of various synthesis methods of nanostructured metal oxide-based semiconductors and their superior gas sensing properties, such as fast response and recovery and a low detection limit towards different hazardous gases.With the prime concern of environmental pollution, a wide range of novel nanostructured metal-oxide based semiconductor gas sensors and their gas sensing properties are interpreted and summarized here.It is essential to measure the sensitivity of the sensors to ensure that they are prepared in a reproducible manner.They must work in ambient conditions andin the presence of humidity. Recent progress in the research and development of metal oxide semiconductor-based gas sensor technology is surveyed in this review. From the bottleneck, this review organizes some prospects that can be expected in future investigations on the gas sensing mechanism of metal oxide semiconductors. 

Nanostructured metal oxide semiconductor-based gas sensors: A comprehensive review

Highly sensitive and selective detection of nitric oxide (NO) has recently attracted much attention due to its environmental pollution and biological role Herein, hierarchical porous ZnO microtubules were simply and massively prepared through zinc salt immersion and air calcination using hemp fiber as biotemplate The effect of different calcination temperature on the microstructure and gas-sensing performance was investigated The ZnO-600 microtubules calcined at 600 °C are assembled from the cross-linking nanoparticles with good crystallinity Especially, the multi-pores and diverse nano-channels are in favor of the quick diffusion and adsorption of target gas, enabling ZnO-600 material to present excellent gas-sensing performance towards trace NO At low working temperature of 92 °C, the sensor fabricated by ZnO-600 microtubules to NO exhibits high response (10 ppm, S = 7854), fast response-recovery, good selectivity as well as satisfactory stability and anti-humidity Meanwhile, this sensor represents the lowest detection limit of 5 ppb (S = 122) among all reported ZnO-based sensors Moreover, the gas-sensing mechanism for ZnO-600 material is demonstrated to be surface adsorption control model

Biomass-derived hierarchical porous ZnO microtubules for highly selective detection of ppb-level nitric oxide at low temperature

Gas sensors based on hybrid materials of graphene oxide/metal oxide semiconductors are an effective way to improve sensor performance. In this paper, we demonstrate a high-performance nitric oxide ...

Observation of Switchable Dual-Conductive Channels and Related Nitric Oxide Gas-Sensing Properties in the N-rGO/ZnO Heterogeneous Structure.

In view of the low sensitivity, high operating temperature and poor selectivity of acetone measurements, in this paper much effort has been paid to improve the performance of acetone sensors from three aspects: increasing the surface area of the material, improving the surface activity and enhancing gas diffusion. A hierarchical flower-like Pt-doped (1 wt %) 3D porous SnO2 (3DPS) material was synthesized by a one-step hydrothermal method. The micropores of the material were constructed by subsequent annealing. The results of the experiments show that the 3DPS-based sensor's response is strongly dependent on temperature, exhibiting a mountain-like response curve. The maximum sensor sensitivity (Ra/Rg) was found to be as high as 505.7 at a heating temperature of 153 °C and with an exposure to 100 ppm acetone. Additionally, at 153 °C, the sensor still had a response of 2.1 when exposed to 50 ppb acetone gas. The 3DPS-based sensor also has an excellent selectivity for acetone detection. The high sensitivity can be explained by the increase in the specific surface area brought about by the hierarchical flower-like structure, the enhanced surface activity of the noble metal nanoparticles, and the rapid diffusion of free-gas and adsorbed gas molecules caused by the multiple channels of the microporous structure.

https://www.mdpi.com/1424-8220/20/4/1150/pdf

Ting Pan

Papers

Observation of Switchable Dual-Conductive Channels and Related Nitric Oxide Gas-Sensing Properties in the N-rGO/ZnO Heterogeneous Structure.

A Highly Sensitive and Selective ppb-Level Acetone Sensor Based on a Pt-Doped 3D Porous SnO2 Hierarchical Structure.